This invention relates to a conference bridge and more particularly to a conference bridge for automatic switching systems.
There are two known types of conference bridges now in use. The first type is an analog conference bridge employing a mixed analog and digital switch. However, this type of conference bridge introduces severe peaks of traffic across the intermatrix units which conferences with several digital subscribers would cause. The second type is a conference bridge based on a digital-to-analog conversion followed by analog mixing and analog-to-digital conversion. In this type of conference bridge, there is employed an encoder/decoder for each conference channel occupying one integrated circuit card. Therefore, if it is required to enable ten conferees in a conference, 10 cards would be required for the encoders/decoders alone. Further, if mixing type conference bridges are connected in tandem to assemble large conference degradation of speech quality would occur because of accumulative quantizing errors.
A copending application of C. R. Brown, Ser. No. 407,686, filed Oct. 18, 1973, assigned to the same assignee as the present application, discloses one form of digital conference bridge overcoming the above-mentioned disadvantages.